Plasma soluble α-klotho protein levels in premature and term neonates: correlations with growth and metabolic parameters

Objective: alpha-Klotho (alpha-KL), a protein with antiaging properties, regulates phosphate, calcium, and bone metabolism, induces resistance to oxidative stress, and may participate in insulin signaling. The role of alpha-KL in neonates, known to be prone to metabolic disturbances and oxidative stress, is not known. The aim of this study was to evaluate circulating soluble alpha-KL concentrations in preterm and full-term neonates and unravel possible correlations with growth, metabolism, and indices of oxidative stress. Design: Prospective study. Methods: Plasma-soluble alpha-KL levels were determined by specific ELISA in 50 healthy neonates (25 preterm, mean (S.D.) gestational age (GA) 33.7 (1.1) weeks, and 25 full-term infants) at days 14 and 28 of life. Associations of alpha-KL with anthropometric, metabolic parameters, and indices of oxidative stress were examined. Results: alpha-KL levels were significantly higher in full-term than in preterm infants at both days 14 (1099 (480) pg/ml vs 884 (239) pg/ml respectively; P<0.05) and 28 (1277 (444) pg/ml vs 983 (264) pg/ml respectively; P! 0.01). In both preterm and full-term infants, alpha-KL levels increased significantly from day 14 to 28 of life (P<0.001). Circulating alpha-KL concentrations correlated with GA (beta=0.32, P=0.001), body weight (beta=0.34, P=0.001), body length (beta=0.33, P=0.001), 1,25-dihydroxy-vitamin D level (beta=0.24, P<0.05), and malondialdehyde level (beta=0.20, P<0.05) but not with glucose, insulin, or homeostasis model assessment index of insulin resistance values. Conclusions: Soluble alpha-KL levels rise as GA and postnatal age advance in neonates and may have an impact on vitamin D metabolism and oxidative stress. Whether alpha-KL may have a role in the regulation of infants' growth should be further studied.